lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <CAGS+omAJaEaGUNY6V=sGNOWHxhb3YRv2mPcuUwQV99ksvsNP4Q@mail.gmail.com>
Date:	Wed, 28 Mar 2012 21:21:42 +0800
From:	Daniel Kurtz <djkurtz@...omium.org>
To:	Chris Wilson <chris@...is-wilson.co.uk>
Cc:	Daniel Vetter <daniel@...ll.ch>, Keith Packard <keithp@...thp.com>,
	David Airlie <airlied@...ux.ie>,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	Benson Leung <bleung@...omium.org>,
	Yufeng Shen <miletus@...omium.org>
Subject: Re: [PATCH 14/14 v5] drm/i915/intel_i2c: remove POSTING_READ() from
 gmbus transfers

On Wed, Mar 28, 2012 at 9:05 PM, Chris Wilson <chris@...is-wilson.co.uk> wrote:
> On Wed, 28 Mar 2012 20:51:57 +0800, Daniel Kurtz <djkurtz@...omium.org> wrote:
>> The POSTING_READ() calls were originally added to make sure the writes
>> were flushed before any timing delays and across loops.
>> However, the normal I915_READ() and I915_WRITE() macros already call
>> readl() / writel(), which already have an explicit mb().
>>
>> Now that the code has settled a bit, let's remove them.
>>
>> Signed-off-by: Daniel Kurtz <djkurtz@...omium.org>
>> ---
>>  drivers/gpu/drm/i915/intel_i2c.c |    5 -----
>>  1 files changed, 0 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c
>> index 2865313..be2852e 100644
>> --- a/drivers/gpu/drm/i915/intel_i2c.c
>> +++ b/drivers/gpu/drm/i915/intel_i2c.c
>> @@ -131,7 +131,6 @@ static void set_clock(void *data, int state_high)
>>                       GPIO_CLOCK_VAL_MASK;
>>
>>       I915_WRITE_NOTRACE(bus->gpio_reg, reserved | clock_bits);
>> -     POSTING_READ(bus->gpio_reg);
> We do need the write flush here (and set_data) as the next action is a
> udelay loop which is not per-se a mb.

Now I am confused.  I915_WRITE_NOTRACE() calls writel(), which has an
explicit mb();  Why do you need another mb?

> -Chris
>
> --
> Chris Wilson, Intel Open Source Technology Centre
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ